The display size of liquid crystal display (LCD) devices, such as liquid crystal televisions, has been increasing in recent years, that is to say, the area of one display region in a liquid crystal panel has been increasing. In addition, the resolution of the LCD devices has been increasing in recent years, that is to say, the number of pixels that form one display region in the liquid crystal display panel has been increasing. When the display size of LCD device increases, a length of data lines (video signal lines) also increases. It causes a delay of video signals within the data lines, which deteriorates an image quality. In order to prevent an image quality from deteriorating, multiple signal input terminals for data lines are provided on the top and bottom of the display region in an LCD device, for example, in recent years.
In the case where signal input terminals for data lines are provided on the top and bottom of the display region, one display region is divided into an upper region and a lower region along a border region in the direction in which gate lines extend. The data lines connected to drains of TFT (thin film transistor) elements of pixels which belong to the upper region above the border region are electrically isolated from data lines connected to drains of TFT elements of pixels which belong to the lower display region below the border region.
In this configuration, images can be displayed side-by-side in the upper region and the lower region. Therefore, since the data lines are divided into two lines, time required to display one frame for an image becomes half compared with the case where the long signal lines are used, and thus, it becomes easy to deal with an increase in the speed of display.
In the above configuration, however, the image quality greatly changes along the above described border region and an undesirable line image may be visible along the border region. In particular, it has been found that a difference in characteristics between a TFT formed around the border region and a TFT formed far from the border region causes the image deterioration such as an undesirable lateral line around the border region.